Aerated fluid drilling process



March 25, 1958 R. A. BOBO AERATED FLUID DRILLING PROCESS Filed June 23, 1955 INVENTOR. R. A. 8080 BY z y FIG 2.

ATTORNEYS United States ,.Patent0 l.

2,828,107 AERATED FLUID DRlLLlNG PROCESS Roy A. BobojI-Iouston, TeiL, assignor to Phil lips letroleum Company, a corporation of Delaware Application June 23, 1955, Serial No. 517,420

Claims. c1. ass- 1.8

This invention relates to an apparatus and process for use in rotary drilling with aerated drilling fluid.

In drilling oil wells, it has been found that using a light weight drilling fluid often increases the drilling rate and reduces the number of bits used, thus decreasing drilling costs. One successful method for obtaining a light weight drilling fluid is to inject air or natural gas into the drilling fluid at the well head. To provide the necessary pressure drop across the drill bit for proper control of the drilling fluid column, it is often necessary to reduce the size and/ or number of jets in the drill bit. However, it is necessary to displace the air or gas-lightened fluid with non-aerated fluid before pulling the pipe from the hole. The reduced area for circulation through the bit decreases the circulation rate, thus increasing the waiting time before pulling the pipe and off-setting some of the savings made by using light weight drilling fluid. My invention comprises a method and apparatus for reducing the lost time while displacing air from the hole.

The principal object of the invention is to provide an improved process and apparatus for rotary drilling with aerated drilling fluid. Another object is to provide a method and apparatus for use in rotary drilling which reduces the time required to replace an aerated drilling fluid in the drill string and well-bore annulus with nonaerated drilling fluid. A further object is to provide a method and apparatus for reducing the lost time in rotary drilling when changing the drilling fluid in the drill string and bore hole from an aerated to a non-aerated type. Other objects of the invention will become apparent from a consideration of the accompanying disclosure.

The invention comprises a method and means for rapidly circulating non-aerated drilling fluid out of the drill string and annulus through circulating conduit means larger in cross sectional area than the cross sectional area of the fluid circulating means in the drill bit. This auxiliary circulating conduit means is positioned above the bit near the end of the drill string and preferably between the lowest drill collar and the drill bit. When making hole, the auxiliary circulating conduit means is closed to the flow of drilling fluid but can easily be opened to such flow when it is desired to displace the aerated drilling fluid in the bore hole.

More complete understanding of the invention may be had by reference to the accompanying schematic drawing of which Figure l is an elevation showing a drill string including the device of the invention; Figure 2 is a longitudinal cross section of the circulating sub of the invention attached to a rotary drill bit; and Figure 3 is a longitudinal cross sectional view of a shearing dart to be used in combination with the circulating sub shown in Figure 2.

The drill string is illustrated in Figure 1 and comprises kelly 10, drill pipe 11, drill collar 12, circulating sub 13 and drill bit 14. Drill bit 14 includes one or more circulating jets 15, while circulating sub 13 includes at least one circulating nozzle 16.

sageway 22'through circulating sub 13 to the-annulus Patented -Mar. 25, 1958 prises a tubular body-21-having a-threadedipin 20 for attachment with drill collar 12. A central passage 22 extendsthroughpin 20 and body 21 and is enlarged or expanded in a lower section 23 to provide operating means for the hereinafter described valve. One'or more ports'or passageways 25 in'thewall of body 21 connect the upper portion of expanded section 23 with circulating nozzle 16 to provide-conduit'means from the axial .pas-

surrounding the drill string. vThe transverse cross sectional area of; ports 25 must be-Fgreater than that ofthe corresponding area of jets 15.- A-tubula'r valve member 26 is: positioned expanded section 23. in engaging relation with the wall thereof and is provided with O-ring seals 28 in its outer cylindrical surface 27 which coopcrate with the cylindrical wall of section 23 to form a seal between central passage 22 and ports 25. Drill bit 14 is provided with a pin 29 which is threaded into the lower end of body 21, and with cones 17 and jets or circulating conduits 15. A ring 30 is attached to the lower end of valve 26 by shear pins 31 so that ring 30 rests on the upper end of pin 29 to maintain valve 26 in the position shown. The upper portion of valve 26 is larger than the lower portion, thus forming a shoulder 34 which is larger in diameter than the central bore of ring 30. Openings 35 through the wall of tubular valve 26 below shoulder 34 serve to equalize the pressure in the annular space between the valve and body member 21 and in the central passageway 22. A shearing dart 36, illustrated in Figure 3, has a seating surface 37 which is machined to form a seal with surface 38 of valve 26.

During normal operations, valve 26 is in the position shown and the circulation of air-lightened drilling fluid is from the usual mud circulation equipment (not shown) into kelly 10, through drill pipe 11 and drill collar 12, passage 22, valve 26, pin 29 and circulating jets 15 and upward within the annular space within the well bore to the surface of the ground. When it becomes necessary to pull the pipe from the well, shearing dart 36 is inserted into the hollow drill string at the surface of the ground and is pumped downward until surface 37 seats on surface 38 thus forming a tight shut off. The force generated by the pressure of the drilling fluid quickly shears pins 31 and forces valve 26 downward until shoulder 34 contacts ring 30. O-ring seal 28 and the top of valve 26 are below ports 25, thus opening a larger area for circulation. The circulation rate is then greatly accelerated without additional pressure, thus reducing the time necessary to displace the air from the hole.

It is apparent that the circulating capacity of ports 25 in the Wall of sub 21 must be substantially larger than that of the jets or circulating means in the drill bit in order to obtain substantial advantage from the invention. It is desirable to construct the sub so that ports 25 are at least 50% greater in transverse cross sectional area than jets 15 and, preferably, at least 3 or 4 times greater. This may be accomplished by making cylindrical conduits 25 larger in diameter and/or more numerous than jets 15.

Certain modifications of the invention will become apparent to those skilled in the art and the illustrative details disclosed are not to be construed as imposing unnecessary limitations on the invention.

I claim: 9

l. A process of rotary drilling with an aerated drilling fluid comprising circulating said fluid through a hollow drill string including-a rotary drill bit on its lower end while rotating said string in an earth bore hole until pulling of said string is desired; thereafter closing said string just above said bit to the flow of fluid, opening at least r .82am? one port in said string above the level of closure, and displacing said fluid through said at least one port at a faster rate than would be effected through said bit at any given hydrostatic head by injecting non-aerated drilling fluid into the upper end of said string until aerated fluid is displaced from said string above said at least one port and from the surrounding annulus; and thereafter pulling said string.

2. The process of claim 1 wherein'said aerated drilling.

fluid comprisesaqueous drilling mud aerated with compressed air.

3. The process of claim 1 wherein said fluid is circulated thru a plurality of said ports.

4. In a process of rotary drillingwith a drilling fluid circulating thru a hollow drill string, including a rotary drill bit on the lower end of'said string,'while rotating said string in an earth borehole until rapid changing of the drilling fluid in said string is desired; the improvement comprising, closing said string just above said bit to the flow of fluid therethru and circulating the fluid in the drill string thru at least one port in said string just above the level of closure at a faster rate than would be effected thru said bit at any given hydrostatic head by injecting a second drilling fluid into the upper end of said string until the original drilling fluid is displaced from said string above said port.

5. A process of claim 4 wherein the drill string and annulus surrounding the drill string are filled with an aerated drilling fluid comprising aqueous drilling mud and compressed air,.'and the second drilling fluid comprises non-aerated aqueous drilling mud.

References Cited in the file of this patent UNITED STATES PATENTS 2,312,018 Beckman Feb. 23, 1943 2,435,016 Pitts Jan. 27, 1948 

